The following is a synopsis of information received via E-mail:
On 4/21/2018 at 1437 AST, the irradiator faulted with a 'Source Pass Cylinder Fault.' Source rack No. 1 moved to safe position in the pool but rack No. 2 remained in the raised position. The Maintenance Manager was notified of the situation. After evaluating the problem with the rack, he found that the air from the source rack No. 2 hoist cylinder was not being released through SVP36 and SVP36A. The Operators loosened a pipe fitting and let air slowly bleed from the rack hoist cylinder. This brought rack No. 2 into a fully lowered position at 1446 AST.
The Maintenance Manager contacted the corporate, Radiation Safety Manager and the plant manager and informed them of the situation.
The Maintenance Manager removed SVP36 and SVP36A valves and took them to the maintenance shop. There was no debris or water found in the valves. Both valves were replaced.
The Maintenance Manager contacted the Plant Manager and the corporate RSM to inform them that the rack problem was caused by the valves not releasing and that valves had been replaced.
The Maintenance Manager restarted the irradiator and after one cycle stopped the irradiator to test the valves. The source racks lowered into the pool as designed.
Corrective Actions:
1. The solenoid valve vendor will be contacted Monday morning and backup-replacement valves for SVP35, SVP35A, SVP36 and SVP36A will be ordered.
2. Annual replacement of SVP35, SVP35A, SVP36 and SVP36A will be added as an annual PM task.
Further investigation into the source valve failure will continue and conclusions will be included in the written report to Region 1 within 30 days.
The irradiator is now operating as designed. No personnel were exposed, nor was there the possibility of exposure, to the source.